Author:

Martin Dressel(1. Physikalisches Institut, Universitat Stuttgart)

While the electronic properties of cuprates can be modified by
electron or hole doping, organic conductors provide the
opportunity to tune the strength of electronic correlations more
directly. Varying the bandwidth by (physical or chemical)
pressure, the $\kappa$-phase BEDT-TTF compounds cross over from a
Fermi liquid to a Mott insulator by increasing effective
correlations. We systematically investigate the electronic
transport properties in organic conductors by dc resistivity and
optical measurements in order to extract the temperature and
frequency-dependent scattering rate $1/\tau = A(k_BT)^2 +
B(\hbar\omega)^2$. We find corresponding temperature and frequency
ranges in which the parabolic behaviors are observed. For the
first time, we can quantitatively relate the two prefactors
($A/B=56$) and their enhancement as correlations increase upon
approaching the Mott transition.
Conceptually low-dimensional organic conductors are also good
candidates for quantum criticality because often an ordered state
is located next to a metallic state when the system is tuned by
pressure. Interestingly both are found, order in the spin as well
as in the charge sector. Fermi-liquid behavior observed in the
metallic state seems to be limited to certain regions of the phase diagram with non-Fermi-liquid properties evolving as the ordered phase is approached. It is not clear whether these deviations from Fermi liquid behavior are actually a signature of quantum criticality.\\[4pt]
[1] M. Dressel,
{\it Quantum criticality in organic conductors? Fermi-liquid versus non-Fermi-liquid behavior},
J. Phys.: Condens. Matter {\bf 23}, 293201 (2011).\newline
[2] S. Yasin, M. Dumm, B. Salameh, P. Batail, C. M{\'e}zi{\'e}re and M. Dressel, {\it Transport studies at the Mott transition of the two-dimensional organic metal} $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br$_x$Cl$_{1-x}$,
Eur. Phys. J. B {\bf 79}, 383 (2011).\newline
[3] M. Dumm, D. Faltermeier, N. Drichko and M. Dressel,
{\it Bandwidth-controlled Mott transition in} $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br$_x$Cl$_{1-x}$: {\it Optical studies of correlated carriers}, Phys. Rev. B {\bf 79}, 195106 (2009)\newpage
[4] J. Merino, M. Dumm, N. Drichko, M. Dressel and R. H. McKenzie, {\it Quasiparticles at the verge of localization near the Mott metal-insulator transition in a two-dimensional material}, Phys. Rev. Lett. {\bf 100}, 086404 (2008)

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2012.MAR.Y3.2